Effect of fabrication conditions on the properties of indium tin oxide powders

This paper reports that indium tin oxide （ITO） crystalline powders are prepared by coprecipitation method. Fabrication conditions mainly as sintering temperature and Sn doping content are correlated with the phase, microstructure, infrared emissivity c and powder resistivity of indium tin oxides by means of x-ray diffraction, Fourier transform infrared, and transmission electron microscope. The optimum sintering temperature of 1350℃ and Sn doping content 6～8wt% are determined. The application of ITO in the military camouflage field is proposed.

Controllable preparation and microwave absorption properties of shape anisotropic Fe_(3)O_(4) nanobelts

To substantially prevent electromagnetic threatens,microwave absorbing materials(MAMs)are required to eliminate surplus electromagnetic waves.As a typical MAM,Fe_(3)O_(4) particles with complex permittivity and permeability have been widely applied due to the coexistence of magnetic loss and dielectric loss.However,the necessary high mass fraction significantly limited its applications,thus Fe_(3)O_(4) nanostructures have been extensively investigated to overcome this problem.In this work,uniform Fe_(3)O_(4) nanobelts were prepared by electrospinning and two-step thermal treatment.By controlling the composition and viscosity of the electrospinning precursor solution,Fe_(3)O_(4) nanobelts with tunable lateral sizes(200 nme1 mm)were obtained.The samples with low content(only 16.7 wt%)Fe_(3)O_(4) exhibited wide maximum effective absorbing bandwidths(EAB)over 3 GHz,and Fe_(3)O_(4) nanobelts with smaller lateral sizes showed a maximum EAB of 4.93 GHz.Meanwhile,Fe_(3)O_(4) nanobelts with smaller lateral sizes presented superior reflection loss properties,the lowest reflection loss reached-53.93 dB at 10.10 GHz,while the maximum EAB was up to 2.98 GHz.The excellent microwave reflection loss of Fe_(3)O_(4) nanobelts was contributed to the enhanced synergistic effect of magnetic loss,dielectric loss,and impedance matching,originated from the hierarchically cross-linked networks and shape anisotropies.This study could broaden the practical applications of magnetic absorbers,and provided an approach for the development of shape anisotropic magnetic materials.

Shape anisotropic Fe3O4 nanotubes for efficient microwave absorption

Although Fe3O4 particles have exhibited excellent microwave absorbing capacity and widely used in practical application due to the synergistic effect of magnetic loss and dielectric loss,their applications are still limited for the required high mass fraction in absorbers.To overcome this problem,the development of Fe3O4 materials with low dimensional structures is necessary.In this study,the shape anisotropic Fe3O4 nanotubes(NTs)with low mass ratios were applied to realize efficient microwave absorption.The NTs with different aspect ratios were prepared through facile electrospinning followed by two-step thermal treatments and mechanical shearing.The cross-linked nanotubular structure enabled the absorbers to have much higher electrical conductivity,multiple scattering,polarization relaxation and better anti-reflection surface,while the shape anisotropic NTs maintained significant multiple resonances with stronger coercivity.These all were beneficial to microwave absorption with enhanced dielectric loss,magnetic loss and sterling impedance matching.Results showed that the absorber with 33.3 wt.%of short Fe3O4 NTs had minimum reflection loss of-58.36 dB at 17.32 GHz with a thickness of 1.27 mm,and had the maximum effective absorbing bandwidth(EAB)of 5.27 GHz when the thickness was 1.53 mm.The absorber with 14.3 wt.%of long Fe3O4 NTs presented the widest EAB in certain radar band with attenuated 80.75%X band and 85%Ku band energy bellow-10 dB at the thickness of 2.65 and 1.53 mm,respectively.This study provided an approach for the development of shape anisotropic magnetic absorbing materials,and broadened their practical applications as magnetic absorbers.

热处理对自反应淬熄法制备低频LiZn铁氧体空心微珠的影响（英文）

目的:自反应淬熄法制备的LiZn铁氧体空心微珠密度小,低频吸波性能良好,但微珠表面晶型生长不充分。对其采用特定热处理工艺不仅可以使晶体充分发育,获得特定晶型,还可以实现对低频吸波性能的有效调控。本文旨在研究热处理工艺对LiZn铁氧体空心微珠表面形貌、相结构和低频吸波性能的影响。创新点:1.通过热处理工艺,实现对LiZn铁氧体空心微珠表面形貌、相结构和低频吸波性能的有效调控;2.深入分析热处理工艺对LiZn铁氧体空心微珠低频吸波性能的改善机理。方法:1.通过工艺探索,确定热处理的详细工艺参数。2.通过扫描电子显微镜检测和X射线衍射分析,获得热处理前后LiZn铁氧体空心微珠的微观形貌(图2)和物相组成(图3)。3.通过矢量网络分析仪,获得热处理前后材料的电磁参数(图4);在此基础上对比其吸波性能(图5),并研究吸波影响机理。结论:1.采用240°C/min升温至1200°C并保温4 h的热处理后,LiZn铁氧体空心微珠表面晶粒明显长大;2.热处理后,微珠四个电磁参数均有所增大,低频吸波性能明显提高,吸收峰值向低频移动;3.表面多种形状微纳米晶粒的形成和长大可能是LiZn铁氧体空心微珠低频吸波性能得以提高的主要原因。